No longer change the level of any logger unless requested explicitly

Ref: pytest-dev#3013

_pytest/logging.py

@@ -82,26 +82,29 @@ def add_option_ini(option, dest, default=None, type=None, **kwargs):
 
 
 @contextmanager
-def catching_logs(handler, formatter=None, level=logging.NOTSET):
+def catching_logs(handler, formatter=None, level=None):
     """Context manager that prepares the whole logging machinery properly."""
     root_logger = logging.getLogger()
 
     if formatter is not None:
         handler.setFormatter(formatter)
-    handler.setLevel(level)
+    if level is not None:
+        handler.setLevel(level)
 
     # Adding the same handler twice would confuse logging system.
     # Just don't do that.
     add_new_handler = handler not in root_logger.handlers
 
     if add_new_handler:
         root_logger.addHandler(handler)
-    orig_level = root_logger.level
-    root_logger.setLevel(min(orig_level, level))
+    if level is not None:
+        orig_level = root_logger.level
+        root_logger.setLevel(level)
     try:
         yield handler
     finally:
-        root_logger.setLevel(orig_level)
+        if level is not None:
+            root_logger.setLevel(orig_level)
         if add_new_handler:
             root_logger.removeHandler(handler)
 
@@ -166,14 +169,10 @@ def clear(self):
     def set_level(self, level, logger=None):
         """Sets the level for capturing of logs.
 
-        By default, the level is set on the handler used to capture
-        logs. Specify a logger name to instead set the level of any
-        logger.
+        :param int level: the logger to level.
+        :param str logger: the logger to update the level. If not given, the root logger level is updated.
         """
-        if logger is None:
-            logger = self.handler
-        else:
-            logger = logging.getLogger(logger)
+        logger = logging.getLogger(logger)
         logger.setLevel(level)
 
     @contextmanager
@@ -259,6 +258,7 @@ def __init__(self, config):
         self.formatter = logging.Formatter(
             get_option_ini(config, 'log_format'),
             get_option_ini(config, 'log_date_format'))
+        self.log_level = get_actual_log_level(config, 'log_level')
 
         if config.getini('log_cli'):
             log_cli_handler = logging.StreamHandler(sys.stderr)
@@ -269,8 +269,7 @@ def __init__(self, config):
             log_cli_formatter = logging.Formatter(
                 log_cli_format,
                 datefmt=log_cli_date_format)
-            log_cli_level = get_actual_log_level(
-                config, 'log_cli_level', 'log_level') or logging.WARNING
+            log_cli_level = get_actual_log_level(config, 'log_cli_level', 'log_level')
             self.log_cli_handler = log_cli_handler  # needed for a single unittest
             self.live_logs_context = catching_logs(log_cli_handler,
                                                    formatter=log_cli_formatter,
@@ -281,8 +280,7 @@ def __init__(self, config):
 
         log_file = get_option_ini(config, 'log_file')
         if log_file:
-            self.log_file_level = get_actual_log_level(
-                config, 'log_file_level') or logging.WARNING
+            self.log_file_level = get_actual_log_level(config, 'log_file_level')
 
             log_file_format = get_option_ini(
                 config, 'log_file_format', 'log_format')
@@ -303,7 +301,7 @@ def __init__(self, config):
     def _runtest_for(self, item, when):
         """Implements the internals of pytest_runtest_xxx() hook."""
         with catching_logs(LogCaptureHandler(),
-                           formatter=self.formatter) as log_handler:
+                           formatter=self.formatter, level=self.log_level) as log_handler:
             if not hasattr(item, 'catch_log_handlers'):
                 item.catch_log_handlers = {}
             item.catch_log_handlers[when] = log_handler

testing/logging/test_reporting.py

@@ -35,7 +35,7 @@ def test_foo():
             logger.info('text going to logger')
             assert False
         ''')
-    result = testdir.runpytest()
+    result = testdir.runpytest('--log-level=INFO')
     assert result.ret == 1
     result.stdout.fnmatch_lines(['*- Captured *log call -*',
                                  '*text going to logger*'])
@@ -58,7 +58,7 @@ def test_foo():
             logger.info('text going to logger from call')
             assert False
         ''')
-    result = testdir.runpytest()
+    result = testdir.runpytest('--log-level=INFO')
     assert result.ret == 1
     result.stdout.fnmatch_lines(['*- Captured *log setup -*',
                                  '*text going to logger from setup*',
@@ -79,7 +79,7 @@ def teardown_function(function):
             logger.info('text going to logger from teardown')
             assert False
         ''')
-    result = testdir.runpytest()
+    result = testdir.runpytest('--log-level=INFO')
     assert result.ret == 1
     result.stdout.fnmatch_lines(['*- Captured *log call -*',
                                  '*text going to logger from call*',
@@ -168,9 +168,9 @@ def test_log_cli_default_level(testdir):
         import logging
         def test_log_cli(request):
             plugin = request.config.pluginmanager.getplugin('logging-plugin')
-            assert plugin.log_cli_handler.level == logging.WARNING
-            logging.getLogger('catchlog').info("This log message won't be shown")
-            logging.getLogger('catchlog').warning("This log message will be shown")
+            assert plugin.log_cli_handler.level == logging.NOTSET
+            logging.getLogger('catchlog').info("INFO message won't be shown")
+            logging.getLogger('catchlog').warning("WARNING message will be shown")
             print('PASSED')
     ''')
     testdir.makeini('''
@@ -185,15 +185,9 @@ def test_log_cli(request):
         'test_log_cli_default_level.py PASSED',
     ])
     result.stderr.fnmatch_lines([
-        "* This log message will be shown"
+        '*WARNING message will be shown*',
     ])
-    for line in result.errlines:
-        try:
-            assert "This log message won't be shown" in line
-            pytest.fail("A log message was shown and it shouldn't have been")
-        except AssertionError:
-            continue
-
+    assert "INFO message won't be shown" not in result.stderr.str()
     # make sure that that we get a '0' exit code for the testsuite
     assert result.ret == 0
 
@@ -307,7 +301,7 @@ def test_log_file(request):
 
     log_file = testdir.tmpdir.join('pytest.log').strpath
 
-    result = testdir.runpytest('-s', '--log-file={0}'.format(log_file))
+    result = testdir.runpytest('-s', '--log-file={0}'.format(log_file), '--log-file-level=WARNING')
 
     # fnmatch_lines does an assertion internally
     result.stdout.fnmatch_lines([
@@ -356,13 +350,24 @@ def test_log_file(request):
         assert "This log message won't be shown" not in contents
 
 
+def test_log_level_not_changed_by_default(testdir):
+    testdir.makepyfile('''
+        import logging
+        def test_log_file():
+            assert logging.getLogger().level == logging.WARNING
+    ''')
+    result = testdir.runpytest('-s')
+    result.stdout.fnmatch_lines('* 1 passed in *')
+
+
 def test_log_file_ini(testdir):
     log_file = testdir.tmpdir.join('pytest.log').strpath
 
     testdir.makeini(
         """
         [pytest]
         log_file={0}
+        log_file_level=WARNING
         """.format(log_file))
     testdir.makepyfile('''
         import pytest